1. Field of the Invention
The present invention relates to a change-over device for changing between a normal photographing position or mode and a macro photographing position of mode for a zoom lens in which zooming operations and focusing operations are both carried out using a single operational barrel of an optical system in which each lens group of the optical system is moved in the macro photographing mode with the spacing between the respective groups being maintained constant.
2. Description of the Prior Art
At the time of change over to macro or close-up photographing, the distance to an object whose focused image is formed on the image plane of the overall optical system remains constant. However, the following points should be taken into consideration in the design of a change-over device. In prior art lens systems of this genaral type, if the focusing operation were to be carried out up to the minimum possible photographing distance to the object, either desirable macro photographing characteristics are not attainable or a desirable image magnification factor is not obtainable. Moreover, it is not possible upon change over to the macro photographing mode to utilize the photographing distance scale provided on the operational barrel. Instead, it is necessary to visually estimate the distance to the object. As the photographic image magnification factor is predetermined, photographing must be carried out according to the image magnification scale indicated on the outside of the lens.
Accordingly, in such a lens, if change over to macro photographing is permitted irrespective of the focusing position of the operational barrel, it is impossible to provide an indication of the distance range for macro photographing on the outside of the lens barrel. For this reason, it is necessary to view a desired image through a camera finder while manually operating the focusing adjustment. This results in poor operationability of the lens.